Django - ORM-many operation table

Create a data table for demonstration

models.py:
                        class Boy(models.Model):
                            name = models.CharField(max_length=32, null=True)

                        class Girl(models.Model):
                            nick = models.CharField(max_length=32, null=True)

                        class Love(models.Model):
                            b = models.ForeignKey("Boy", null=True)
                            g = models.ForeignKey("Girl", null=True)

A corresponding query boy girl boy table

method one

# RES = models.Boy.objects.filter (name = 'boy1'). First () 
# # Print (RES) 
### Boy Object 
# ### records in a reverse lookup love 
# love_list = res.love_set. All () 
## <QuerySet [<Love: Love Object>, <Love: Love Object>]> 
# for obj in love_list: 
#      ### forward lookup table girl Nick 
#      Print (obj.g.nick)

Method Two

# res = models.Love.objects.filter(b__name='勾洋').all()
# print(res) ## <QuerySet [<Love: Love object>, <Love: Love object>]>
# for obj in res:
#     print(obj.g.nick)

Method Three

res = models.Love.objects.filter(b__name='勾洋').values("g__nick")
print(res)

The above method is based on the third-many table to create our own terms associated with the two tables together to achieve positive check pegging

In django, we can generate a third table by ManyToManyField ()

在models.py下
class Boy(models.Model):
　　name = models.CharField(max_length=32, null=True)
　　g = models.ManyToManyField('Girl', null=True)

class Girl(models.Model):
　　nick = models.CharField(max_length=32, null=True)

increase

= models.Boy.objects.filter obj (name = 'boy1 ' ) .first ()
 Print (obj) 
# ==> Boy Object 
obj.g.add (. 3) 
obj.g.add (* [1,2] ) add two data relation table

Reset

obj = models.Boy.objects.filter(name='boy1').first()

obj.g.set ([4]) all relevant data obj clear association table and rewrites data list

Inquire

obj = models.Boy.objects.filter(name='boy1').first()
res = obj.g.all()
print(res)
#==》<QuerySet [<Girl: Girl object>, <Girl: Girl object>, <Girl: Girl object>]>
for obj  in res:
     print(obj.nick)

delete　　

obj = models.Boy.objects.filter(name='boy1').first()
obj.g.clear()

Django - ORM-many operation table

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